Electric valve control circuit



J ly 7, 1942.

C. C. HERSKIND ELECTRIC VALVE CONTROL CIRCUIT Filed March 26, 1941Inventor: Carl C Herskind by His Attorney.

Patented July 7, 1942 UNE'EED STATE FA'EENT FFEQE ELECTRIC VALVECUN'ERQL cmcnicr Carl C. Hersklnd, Schenectady, N. E, aesignor toGeneral Electric Company, a corporation of New York Application March26, 1941, Semi" No. 385,275

7 Claims.

ing immersion-igniter control members or makealive electrodes. In thistype of electric valve means a control member is associated with acathode and preferably has an extremity of a control. member extendinginto the cathode which may be a mercury pool. The immersionignitercontrol member is preferably constructed of a material having anelectrical resistivity which is large compared with that ottheassociat'ed cathode, and an arc discharge is established between theanode and cathode of the electric valve means by transmitting throughthe control member to the cathode a current of predetermined valuesufficient to establish at the surface of the mercury a potentialgradient of proper magnitude to effect ionization of the mercury vapor.In accordance with the teachings of my invention described hereinafter,I provide a new and improved control circuit for electric valveapparatus of the above described type.

It is anobject of my invention 'to provide a new and improved electriccontrol circuit.

It is another object of my invention to provide a new and improvedexcitation circuit for electric discharge valves.

It is a further object of my invention to pro,- vide a new and improvedcontrol circuit for electric valve apparatus of the type employing animmersion-igniter type control member in which the life oi an electricvalve is substantially increased by reduction of the current which theimmersion-igniter' control is required to transmit and which ischaracterized by its simplicity and reliability in operation.

' In accordance with the illustrated embodiment of my invention, Iprovide a control or excitation circuit for electric valve means emfroma polyphase alternating current supply.

ploying an immersion-igniter control member which interconnects analternating current; and

a direct current circuit. The conductivities oi.

voltage is produced by a synchronous type dyname-electric machine whichis driven by a synchronous machine having one winding thereof energizedfrom the alternating current circuit with which the electric valves areassoelated. A mechanical distributor mounted on the some shaft with thesynchronous motor and synchronous generator is arranged to connect thealternating current winding of the synchronous type machine with theimmersionigniter control members in succession to energize the controlmember with one halt-wave oi! the harmonic current output of thesynchronous generator. The motor is provided with a main field and aquadrature fieldwhich are energized from a direct current controlcircuit. 2 By providing means for controlling the relative tratedarrangement embodying applicant's invention is characterized by the useof standard equipment of simple construction and reliable operatingcharacteristics.

My invention will be better understood by reference to the followingdescription taken in connection with the accompanying drawing and itsscope will be pointed out in the appended claims. In the drawing Fig. 1is a schematic representation of one embodiment of my invention, andFig. 2 illustrates the voltage waves of the alternating current circuitinterconnected by the electric valve apparatus and the alternatingcurrent voltage wave of the synchronous generator. I

Referring now to Fig. 1 of the drawing, I

.have diagrammatically illustrated my invention as applied to polyphaseelectric valve converter for energizing a direct current load circuit Idcircuit H through electric valve translating apparatus comprising atransformer l2 having a delta connected primary winding I3 energizedfrom the alternating current supply circuit H,

and a six-phase forked-Wye secondary winding H with the end terminals ofwhich are associated a plurality of electric valve means l520.' I 4 Theelectric valve means l520 are of the type including an envelope havingan ionizable medium such as a gas or vapor contained therein and eachincludes an' anode 2|, a cathode 22 which is preferably of theself-reconstructing type, such as a mercury pool cathode, a make-aliveor immersion-igniter control member 23. As is well understood by thoseskilled v side of the armature winding 40.

in the art, the electric valves I-20 may be renderedv conductivesuccessively by transmitting to its associated control member current ofa predetermined value.

In accordance with the teachings of my invention I provide an improvedarrangement for supplying current of the required magnitudeto thecontrol electrode 23 of the valves iiiin succession for a limited timeso that the current carrying duty of the immersion-igniter controlelectrode is materially reduced and the eflfective life of the valvemeans is thereby increased. In the embodiment illustrated this isaccomplished by energizing the igniter froma source of harmonic voltagehaving a frequency equal to the frequency of the alternating currentcircuit multiplied by the number of phasesof the elec- .electrodes ofthe electric valves |520.

and 25 to connect together the contacts 4| and 42 of each pair insuccession .and thereby sequentially complete the circuit of the controlThe stationary contacts 4| and 42 are of such a length that they areshorted by the member 44 for-the duration of one half-cycle of theharmonic voltage induced in the winding .0.

' each control electrode 43 is energized during one tric valveconverting system and utilizing one- The driving motor 24 comprises athree-phase winding 28 energized from the alternating current circuit Hand a field member 23 having pole pieces arranged in quadrature relationand energized from windings 30 and 3|. The field windings 30 and 3| areconnected to the slip rings 32 and 33 which are energized from asuitable source of direct current 34 through variable resisters 35 and36, respectively. By suitable adjustment of resistors 35 and 36 therelative strength of a field produced by windings 30 and 3| may becontrolled and the mechanical position of field structure 29 relative tothe rotating field produced by the winding 28 may m adjusted. Thealternating current generator 25 comprises a rotating field structure 31which, in the particular arrangement disclosed, is a twelve-polestructure having a field winding 38 connected with the slip rings 39.The slip rings may be energized from any suitable source of directcurrent such as the circuit 34. The generator 25 is provided with asingle-phase armature winding 40 in which is induced an alternatingvoltage having a frequency six times the frequency of the alternatingcurrent supply circuit II and having a definite phase relation withrespect thereto. In. order that successive positive halfwaves of thevoltage of the winding 40 may be impressed on the control members 23 ofsuc-.

- cessiv'e ones of the valves |5-20, the distributor mechanism 26 isprovided with a plurality of pairs of fixed contacts 4| and 42. Fixedcontacts 4| are all connected together and to one The other side of thearmature winding is connected to the side of the direct current circuitwith which the cathodes of the electric valve means |5--20 areassociated by means of a conductor 43. Each of the stationary contacts42 is connected to a different one of the control members 23 of theelectric valves |52|l. The distributor mechanism-26 is provided with amovable member 44 of conducting material which is driven synchronouslywith the dynamo-electric machines 24 half-cycle only of the harmonicvoltage. Inasmuch as the "contacts 4| and 42 areshort circuited forexactly one-half cycle of the harmonic voltage the circuits may be madeand broken at current and voltage zero.

In Fig. 2 the voltage of one phase of the circuit H is indicated by thecurve E11 while the harmonic voltage induced in the winding 40 isindicated by the curve E411. It will be noted that the voltage of thewinding 40 is a sixth harmonic and the electric valve converting systemis a six-phase rectifier. It is possible to operate a twelve-phaserectifier in accordance with my invention with a sixth harmonic controlvoltage and in this case the switching mechanism controlling the time atwhich the control members I 23 are energized from vthe winding 40 mustbe arranged so that successive half-cycles of the harmonic voltage willbe impressed on successive electric valves. With the arrangementdisclosed, however, successive positive half-cycles only are utilizedand with this arrangement the switching operation is facilitated. It isapparent that my invention can be carried out utilizing any suitableharmonic which has a number-of half-waves equal to times the half-wavesof the alternating current circuit II where K is an integer and N is thenumber of phases of the electric valve converting system. The systemprovided has numerous advantages from the cost and reliabilitystandpoint, inasmuch as standard rotating equipment may be utilized. Theharmonic generator and the synchronous driving motor may both be anystandard construction. The distributor mecha' nism 26 may also be ofstandard construction.

The quadrature field adjustment of the synchronous motor 28 provides avery simple and effective manner of adjusting the phase of theexcitation of the immersicn-igniter control elec trodes so that thevoltage or current of the direct current circuit may be controlled,automatically if desired.

While I have shown and described a particular embodiment of myinvention, it will be obvious to those skilled in the art that changesand modifications may be made without departingfrom my invention and I,therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by of supporting an arcdischarge and each comprising an anode, a cathode and animmersionigniter control member, said electric valve means beingarranged to conduct current in succession to form an n-phase electricvalve convertingsys- Thus tem, an excitation circuit for energizing theontrol electrodes of said electric valve means comprising .a synchronousgenerator for generating a harmonic voltage having a frequency of ntimes the frequency of said alternating current circuit, and mechanicalswitching means operated-synchronously with said harmonic generator toimpres alternate half-waves of said harmonic voltage on diiferentpnes ofsaid control members in succession.

2. In combination, a pair of circuits, at least one of said circuitsbeing an alternating current circuit; electric translating apparatusconnected between said circuits and including a plurality of electricvalve means of the type employing an ionizable medium capable ofsupporting an arc discharge and each comprising an anode, a cathode andan immersion-igniter control member, said electric valve means beingconnected to provide an n-phase electric valve converter, a controlcircuit for energizing the control electrodes of said electric valvemeans comprising a source of harmonic voltage having a frequency equalto n times the frequency of said alternating current circuit, and meansfor impressing alternate halfwaves of said harmonic voltage onsuccessive ones. of said control electrodes to render said electricvalve means conductive in succession.

3. In combination, a pair of circuits, at least one of said circuitsbeingan alternating current circuit, electric translating apparatusconnected between said circuits and including a plurality of electricvalve means of the type employing an ionizable medium capable ofsupporting an arc discharge and each comprising an anode, a cathode andan immersion-igniter control member, said electric valve means beingconnected to form an n-phase electric valve converting system, a.

control circuit for rendering said electric discharge valve meansconductive in succession comprising a single-phase source of harmonicvoltage having a frequency equal to at least times the frequency of saidalternating, current circuit, and mechanical switching means forcompleting a circuit between said source of harmonic voltage and each ofsaid control members in succession, each of said circuits beingcompleted for the duration of one half-cycle of said harmonic voltage.

4. In combination, an alternating circuit, a direct current circuit,electric translating apparatus connected between said circuits andincluding a plurality oi electric valve means of the type employingan-ionizable medium capable of supporting an arc discharge and eachcomprising an anode, a cathode and a control member, said electric valvemeans being arranged to conduct current in succession to form an n-phaseelectric valve converting system, an excitation circuit for energizingthe control electrodes of said electric valve means comprising asynchronous generator a single-phase source of harmonic voltagehaving afrequency equal to at least timesthe frequency of said alternatingcurrent 70 circuit, and means for. impressing selected differenthalf-waves of said harmonic voltage on the control members of saidelectric valve means in succession in the order in which they are to 'berendered conductive.

5. In combination, an alternating current circuit, a direct currentcircuit, electric translating apparatus connected between said circuitsand including a plurality of electric valve means of a type employing anionizable medium capable of supporting an arc discharge and eachcomprising an anode, a cathode and an immersion-igniter control member,a synchronous generator having a single-phase armature winding forproducing a voltage which is a' harmonic of the voltage of saidalternating current circuit, and switching means operating insynchronism with said synchronous generator for impressing predeterminedhalfwaves of said harmonic voltage on the control members of successiveones of said valves to render said valves conductive in a predeterminedsequence.

6. In combination, an alternating current supply circuit, a directcurrent load circuit, an n-phase electric valve rectifying systeminterconnecting said circuits including a plurality of electric valvemeans of the type employing an ionizable medium capable of supporting anarc discharge and each comprising an anode, a cathtimes the frequency ofsaid alternating. current.

supply circuit, and electric switching means for connecting successivelythe control electrodes of said electric valve means with said armaturewinding to impress thereon predetermined halfwaves of said harmonicvoltage.

7. In combination, an alternating current circuit, a direct currentcircuit, electric translatin apparatus connected between said circuitsand including a plurality of electric valve means of the type employingan ionizable medium capable of supporting an arc discharge and eachcomprising an anode, a cathode and an immersion-igniter control member,a synchronous motor energized from said alternating current circuit,said valve means being connected to form an n-phase elec-- tric valveconverter, a synchronous type generator driven by said synchronousmotor, said synchronous generator having a single-phase armature windingand a field structure having a numberof poles dependent upon the numberof phases of said electric translating apparatus to produce an nharmonic voltage in said single-phase winding, mechanical distributormeans driven by said synchronous motor for controlling the applicationof the voltage of said armature winding to said control electrodes, saiddistributor being arranged to impress alternate half-waves of saidharmonic voltage on diflerent ones of said control electrodes and forimpressing every nth alternate half-wave on the same control electrode.J 4

' CARL C. HERSHND.

